The present invention relates to wedges of the type used to spread a wooden handle within a tool head to secure the head firmly on the end of the handle. More particularly, the present invention is related to a cylindrical wedge that has unique features to improve the holding force of the wedge.
Cylindrical wedges are known in the art for securing tool heads on wooden handles. Such wedges are typically made in screw machines and have a configuration corresponding generally to that shown in FIG. 1. The prior art wedges have a tapered cylindrical configuration on the exterior surface and a straight-walled central bore extending between opposite ends of the wedge except for a small chamfer which defines the cutting edge at the narrow end. The tapered exterior surface is utilized to spread the wooden handle in the eye of a tool, and in order to secure the wedge more firmly within a handle, it is common to provide sharp-edged undercuts or circumferential grooves in the tapered exterior surface for increased friction.
The prior art cylindrical wedges are relatively expensive to make and require a substantially greater amount of raw material than appears in the finished product when made on a screw machine. Additionally, the straight inside wall of the central bore only compresses the core of the wooden handle by a limited amount and does not contribute significantly to the holding force which prevents the wedge from being dislodged from the handle. Also, the grooves in the tapered exterior surface are recessed below the surface, and as a result, wood fibers in the handle can bridge the grooves with only limited increases in the retention forces.
It is accordingly an object of the present invention to provide an improved cylindrical wedge that develops significant holding forces on the tool head and high retention forces on the wedge itself. It is a further object to provide a cylindrical wedge which can be manufactured at reduced cost with less waste of raw material.